质子交换膜燃料电池可靠性分析

可靠性是质子交换膜燃料电池(PEMFC)的重要指标，文中定性分析了PEMFC组成元件、装配工艺和工作过程的可靠性。提出了提高PEMFC可靠性的措施和可靠性的设计原则。     

Non-noble metal oxygen reduction electrocatalysts based on carbon nanotubes with controlled nitrogen contents

Nitrogen-doped carbon nanotubes (CN_x) were prepared via a floating catalyst chemical vapor deposition method using precursors consisting of ferrocene and melamine to control the nitrogen content. Structure, morphology and composition of all CN_x catalysts were characterized by SEM, TEM, and XPS. These results indicated that the surface nitrogen content (up to 7.7 at.%) increases with the increase of melamine used. Electrochemical methods were used to study the correlation between surface structure and the activity of oxygen reduction reaction (ORR) in acid and alkaline solutions. Electrochemical data indicated that the higher the nitrogen content is, the higher the oxygen reduction activity. Especially, the results from the rotating ring disk electrode technique demonstrated that CN_x (7.7%) has similar ORR activity and selectivity with commercial Pt/C in alkaline solution.     

PtFe alloy catalyst supported on porous carbon nanofiber with high activity and durability for oxygen reduction reaction

To reduce the high cost of oxygen reduction reaction (ORR) catalyst and improve the performance of the proton exchange membrane fuel cell (PEMFC), low-Pt or non-Pt catalysts have been studied in recent years. In this paper, PtFe alloy nanoparticles are loaded on porous carbon nanofiber (PCNF) via one-step modified glycol reduction method by adjusting solution pH. On the surface of PCNF, PtFe alloy nanoparticle can be uniformly dispersed with a narrow particle size distribution. The catalyst Pt_4.8Fe/PCNF prepared in pH = 7 solution with PCNF as carbon support exhibits better ORR performance, which shows even 18 mV higher onset potential than that of commercial catalyst Pt/C (Johnson Matthey, JM20). Moreover, comparable durability is also obtained through accelerated durability test (ADT) test after 2000 cycles. The excellent performance of Pt_4.8Fe/PCNF catalyst may attribute to the structural and electronic effects of transition metal in the PtFe alloy. The rough surface and porous structure of PCNF is also supposed to be beneficial for performance improvement.     

Promising nature-based nitrogen-doped porous carbon nanomaterial derived from borassus flabellifer male inflorescence as superior metal-free electrocatalyst for oxygen reduction reaction

In this present study, novel hierarchical nitrogen-doped porous carbon for use as a metal-free oxygen reduction reaction (ORR) electrocatalyst is derived from borassus flabellifer male inflorescences by calcining at 1000 °C in an inert atmosphere using metal hydroxides as activating agent and melamine as nitrogen doping agent. The BET surface areas of the lithium-ion (Li-ion), potassium-ion (K-ion) and calcium-ion (Ca-ion) activated carbon are observed to be 824.02, 810.88 and 602.88 m² g^-1 respectively. Another interesting fact is that the total surface energy calculated by wicking method (73.2 mJ/m²), is found to be higher for Li-ion activated carbons. Among the prepared nitrogen-doped porous carbon, Li-ion activated system, showed an outstanding performance in ORR reaction in alkaline medium, thanks to its high surface area and notable surface activity. An incontrovertible of note that ORR half-wave potential of Li-ion activated nitrogen-doped carbon (0.90 V) is relatively higher in comparison to the commercial 20 wt % Pt/C catalyst (0.86 V). Inspite of overwhelming performance, the ORR reaction followed the preferred 4- electron transfer mechanism involving in the direct reduction pathway in all activated carbons. The ORR performance is also noticeably better and comparable to the best results in the literature based on biomass derived carbon catalysts.     

The synergy between multi-wall carbon nanotubes and Vulcan XC72R in microporous layers

In this study, the effects of the addition of multi-wall carbon nanotubes (MWCNTs) into a microporous layer (MPL) containing Vulcan XC72R on the oxygen reduction reaction (ORR) were studied. We tested various percentages of MWCNTs and Vulcan XC72R in the MPLs of gas-diffusion electrodes (GDEs) with various Pt loadings in the catalyst layer. The performance of the ORR in the electrodes was studied with linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry. The structures of the MPLs were investigated by using scanning electron microscopy (SEM), mercury porosimetry (MP), and gas permeability. In addition, the optimum polytetrafluoroethylene (PTFE) content of the MPL was determined. Our results indicate that the performances of the GDEs are optimal under the following conditions: (a) 60 wt% MWCNTs and 40 wt% Vulcan XC72R with a Pt loading of 0.115 mg/cm²; (b) 80 wt% MWCNTs and 20 wt% Vulcan XC72R with a Pt loading of 0.5 mg/cm²; and (c) 40 wt% MWCNTs and 60 wt% Vulcan XC72R with a Pt loading of 1 mg/cm².     

阴极开放式质子交换膜燃料电池实验性研究

文中围绕实验室自制的开放式阴极自增湿型质子交换膜燃料电池开展了大量相关实验,采用FLUKE Ti25红外温度成像仪测得了各种操作条件下电池表面温度分布图像。实验结果表明:在封闭式阳极(anode dead-end)操作条件下,液态水会在阳极逐渐积累而影响反应气的传质,造成电池输出性能的衰减。通过阳极排气可以使电池性能恢复。纵观电堆表面温度分布情况,总体呈现出沿氢气流道方向递增的趋势。且随着电流密度的增大,这种温度分布的不均匀性变得更加明显。在实验所测试的范围内,电堆的平均输出功率密度达到了583 mW/cm2。     

Optimization of the amount of Nafion in multi-walled carbon nanotube/Nafion composites as Pt supports in gas diffusion electrodes for proton exchange membrane fuel cells

The Nafion loading in multi-walled carbon nanotube (MWCNT) composites with Nafion used as Pt support in the oxygen reduction reaction (ORR) has been studied. We varied the amount of Nafion in these composites and added a Pt loading of 0.3 mg cm⁻² to the catalyst layer. The performance of these electrodes in the ORR was measured with linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), chronoamperometry, inductive coupled plasma (ICP), X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). In addition, we compared the performance of the MWCNTs as Pt supports with those of the composites. Our results indicate that the composites are better Pt supports in comparison with MWCNT.     

质子交换膜燃料电池非贵金属催化剂研究进展

贵金属铂（Pt）基催化剂价格昂贵且易中毒,这是造成质子交换膜燃料电池难以大规模商业化的主要原因,而非贵金属催化剂有望替代Pt基催化剂来解决这一难题。本文综述了最近几年非贵金属催化剂在质子交换膜燃料电池中应用的研究进展,并提出了今后的研究重点和方向。     

Highly efficient electrocatalysts for oxygen reduction reaction: Nitrogen-doped PtNiMo ternary alloys

The relatively low efficiency of the reaction of oxygen reduction (ORR) remains among the main obstacles for hydrogen fed proton exchange membrane fuel cells (H-PEMFCs) commercialization.In the present work, PtNiMo ternary alloy catalysts are obtained through reducing by NaBH₄ and subsequent thermal annealing in NH₃ at 1.0 atm. The as prepared catalysts are physico-chemically (XRD, TEM and XPS) characterized, exhibiting alloy nanostructure.From the electrochemical tests it is found that they exhibit high ORR activity in aqueous solutions saturated with O₂ and acidified with HClO₄. From the as synthesized catalysts, Pt₃Ni₃MoN/C shows the highest mass activity (539.41 mA mg⁻¹ Pt); 3.5 times greater than that observed over commercial Pt/C (154.46 mA mg⁻¹ Pt). Moreover, they show very good stability, while their ORR activity is only slightly altered after 5,000 cycles.These highly performing and low cost catalysts could thus open up new possibilities for the commercialization of hydrogen fed PEMFCs.     

Non-platinum cathode catalyst layer composition for single Membrane Electrode Assembly Proton Exchange Membrane Fuel Cell

The performance of nano-structured templated non-platinum-based cathode electrocatalysts for proton exchange membrane fuel cells (PEMFC) was evaluated for different catalyst layer compositions. The effect of non-platinum catalyst, Nafion, and 35 wt% Teflon modified Vulcan XC-72 Carbon Blacks (XC-35) loadings were measured under H₂/air and H₂/O₂ conditions. Transport hindrances that occur in the catalyst layers are evaluated with ΔE vs. i analysis. It is shown that transport limitations in the cathode catalyst layer can limit the performance of the cell at relatively low current densities if the catalyst layer composition is not optimized. Further, a procedure is outlined here to aid in the implementation of non-traditional catalyst materials into fuel cell systems (i.e. templated electrocatalyst as compared to the standard supported material).     

千瓦级质子交换膜燃料电池电堆的实验研究

空泡率是汽液两相流动的基本参数之一,而已有过冷沸腾空泡率计算方法研究以高质量流速为主。且大量文献报道现有空泡率模型难以适用于低流速过冷沸腾工况。该文基于低流速过冷沸腾净蒸汽产生点(NVG)理论模型,进一步建立了计算过冷沸腾空泡率的分布拟合模型。在较宽广的压力、质量流速、热流密度和流道尺寸范围内将模型计算结果与现有空泡率实验数据进行了比较,低流速工况下该模型与实验数据符合良好,表明该模型可适用于低流速过冷沸腾工况。     

Characterization of Pt supported on commercial fluorinated carbon as cathode catalysts for Polymer Electrolyte Membrane Fuel Cell

Pt nanoparticles supported on carbon monofluoride (CFx), synthesized from H₂PtCl₆ using NaHB₄ as a reducing agent has been investigated as a cathode electrocatalyst in fuel cells. Surface characterization, performed by transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD), shows a homogeneous distribution and high dispersion of metal particles. Kinetic parameters for the electrocatalyst are also obtained from the steady state measurements using a rotating disk electrode (RDE) in 0.5 M H₂SO₄ solution. Analysis by Koutecky–Levich equation indicates an overall 4 e^? oxygen reduction reaction (ORR). Evaluation of the catalyst in single cell membrane electrode assemblies (MEAs) for proton exchange membrane based Direct Methanol Fuel Cell (DMFC) and H₂ Fuel Cell at different temperatures and flows of O₂ and Air are shown and compared against commercial Pt/C as the cathode electrocatalyst. Evaluation of Pt/CFx in H₂ fed fuel cells shows a comparable performance against a commercial catalyst having a higher platinum loading. However, in direct methanol fuel cell cathodes, an improved performance is observed at low O₂ and air flows showing up to 60–70% increase in the peak power density at very low flows (60 mL min^?1).     

Effect of pretreatment on Pt–Co/C cathode catalysts for the oxygen reduction reaction

Carbon supported Pt and Pt–Co electrocatalysts for the oxygen reduction reaction in low temperature fuel cells were prepared by the reduction of the metal salts with sodium borohydride and sodium formate. The effect of surface treatment with nitric acid on the carbon surface and Co on the surface of carbon prior to the deposition of Pt was studied. The catalysts where Pt was deposited on treated carbon the ORR reaction preceded more through the two electron pathway and favored peroxide production, while the fresh carbon catalysts proceeded more through the four electron pathway to complete the oxygen reduction reaction. NaCOOH reduced Pt/C catalysts showed higher activity that NaBH₄ reduced Pt/C catalysts. It was determined that the Co addition has a higher impact on catalyst activity and active surface area when used with NaBH₄ as reducing agent as compared to NaCOOH.     

One-pot synthesis of Pt/CeO2/C catalyst for improving the ORR activity and durability of PEMFC

Oxygen reduction reaction (ORR) activity and durability of Pt catalysts should be both valued for successful commercialization of proton exchange membrane fuel cells (PEMFCs). We offer a facile one-pot synthesis method to prepare Pt/CeO₂/C composite catalysts. CeO₂ nanoparticles, with high Ce³⁺ concentration ranging from 30.9% to 50.6%, offers the very defective surface where Pt nanoparticles preferentially nuclear and growth. The Pt nanoparticles are observed sitting on the CeO₂ surface, increasing the PtCeO₂ interface. The high concentration of oxygen vacancies on CeO₂ surface and large PtCeO₂ interface lead to the strong PtCeO₂ interaction, effectively improving the ORR activity and durability. The mass activity is increased by up to 50%, from 36.44 mA mg^?1 of Pt/C to 52.09 mA mg^?1 of Pt/CeO₂/C containing 20 wt.% CeO₂. Pt/CeO₂/C composite catalysts containing 10–30 wt.% CeO₂ loss about 80% electrochemical surface area after 10,000 cycles, which is a fivefold enhancement in durability, compared to Pt/C losing 79% electrochemical surface area after 2000 cycles.     

Model-based aging tolerant control with power loss prediction of Proton Exchange Membrane Fuel Cell

Proton Exchange Membrane Fuel Cells are promising energy converters that allow powering vehicles or buildings in a clean manner. Nevertheless, their performance are affected by faults and irreversible degradation mechanisms that are far from being fully understood. Consequently, during the last decade, researches have been conducted on the diagnostic of faults of this promising converter. Nevertheless, aging was never the subject of a particular attention concerning control. As a result, this paper proposes an aging tolerant control strategy for Proton Exchange Membrane Fuel Cells. It aims at generating the load current reference taking the state of health into account. Moreover, using a model inversion of an Energetic Macroscopic Representation with time-varying parameters, the coherent references of input flows of gas can be calculated. Finally, the paper details a method to identify and predict the maximum power the fuel cell is able to provide at present time based on a Maximum Power Point Tracking algorithm. Also this algorithm aims at forecasting the Remaining Useful Life for a given power reference. This method is validated on a simulation case.     

Highly active and durable carbon support Pt-rare earth catalyst for proton exchange membrane fuel cell

Pt-rare earth catalysts are highly efficient novel electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) due to their high stability and activity. In this study, we prepare Pt-YO_x/C catalysts using the traditional wet chemical reduction method. The optimal quantity of Y-oxides loaded onto the Pt/C surface is determined based on electrochemical performance using linear sweep voltammetry (LSV) and cyclic voltammetry (CV) methods. After accelerated durability tests (ADT), the remnant electrochemical surface area (ECSA) and mass active (MA) in Pt-YO_x/C catalyst are relatively higher compared to the commercial Pt/C (JM). In the single-cell test, the maximum mass power densities of the MEAs prepared by self-made Pt-YO_x/C and Pt/C (JM) catalysts in cathodes record at 1895 and 1371 mW mg_Pt⁻¹, respectively, which shows a successful increment in platinum utilization. These results indicate that Pt-YO_x/C catalyst can potentially improve the durability and lower the cost of PEMFCs.     

Highly efficient supported PtFe cathode electrocatalysts prepared by homogeneous deposition for proton exchange membrane fuel cell

A simple and efficient approach has been developed for the synthesis of carbon-supported binary PtFe (50:50) electrocatalyst with high metal loading that combines homogeneous deposition (HD) of PtFe hydroxide complex species through generation of OH⁻ ions realized by in situ hydrolysis of urea and subsequent uniform reduction of the complex by ethylene glycol (EG) in a polyol process, providing control over the size and dispersion of PtFe nanoparticles (NPs). Compared to PtFe catalysts prepared with other common synthesis methods using NaBH₄ and EG and commercial PtFe catalyst, the supported PtFe catalyst prepared by the HD-EG method reveals more uniform homogenous dispersion of PtFe NPs with much smaller particle size, thus demonstrating excellent electrocatalytic ability and fuel cell performance. The structural properties and catalytic activities of Pt–Fe catalysts prepared in various synthesis methods were evaluated on the basis of the analysis of HR-TEM, HR-SEM, XRD, electrochemical surface area and fuel cell polarization performance.     

A facile synthesis of Pd/C cathode electrocatalyst for proton exchange membrane fuel cells

A carbon supported palladium (Pd/C-NaBH₄-NH₃) catalyst was synthesized via modified sodium borohydride reduction method using ammonia as the complexing reagent. The Pd/C catalysts were characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). Rotating disk electrode (RDE), cyclic voltammetry (CV), electrochemical impedance spectra (EIS) and single cell measurements were employed to evaluate the activities of the catalysts. The as-prepared catalysts with face-centered cubic (fcc) structure are uniformly dispersed on the carbon supports. Twinned and polycrystalline structures are observed in the HRTEM image of Pd/C-NaBH₄-NH₃. The results indicate that the Pd/C-NaBH₄-NH₃ catalyst shows high activity for the oxygen reduction reaction. Single cell with Pd/C-NaBH₄-NH₃ as the cathode displays a maximum power density of 508 mW cm⁻². The favorable performance of the Pd/C-NaBH₄-NH₃ catalyst may be attributed to the uniformly dispersed nanoparticles and more crystalline lattice defects.     

PEMFC分布式发电系统动态协调控制仿真

符号表m-质量/kg W-质量流量/kg·s-1N-电池个数I-电流/AM-摩尔分子质量F-法拉第常数/kg·mol-1/9.6 487×104C·mol-1R-气体常数/J·(mol·K)-1T-温度/KV-体积/m3A-反应面积/m2nd-电渗透系数Dw-扩散系数/m2·s-1cwa、cwc-膜阳极侧和阴极tm-膜厚度/m侧的水浓度/mol·m-2kp-水力     

Efficient synthesis of Pt3Co/NC alloy catalysts with enhanced durability and activity for the oxygen reduction reaction

Lack of catalytic performance, short life, and high cost are three main problems related to JM-Pt/C catalysts for proton exchange membrane fuel cells. The introduction of cheap transition metals improves catalytic performance while significantly reducing the cost of the catalysts. Here, we report the synthesis of Pt₃Co/NC alloy catalysts via coating and pyrolysis treatment. The agglomeration of nanoparticles during the high-temperature alloying process is significantly inhibited by coating with PANI. Remarkably, the obtained Pt₃Co/NC alloy catalysts exhibit excellent ORR catalytic performance and structural stability in 0.1 mol/L HClO₄. After 30,000 potential cycles, the mass activity and area-specific activity of Pt₃Co/NC alloy catalysts are 1.949 and 3.936 times higher, respectively, than that of JM-Pt/C with negligible performance loss. The strong metal-support interaction between N and Pt and the Pt-rich surface restrict the dissolution of Pt and Co, resulting in excellent stability. This synthesis approach provides an effective way to develop active and stable Pt alloy catalysts.